Recently, the television broadcasting by use of artificial satellites is becoming pervasive. As shown in FIG. 1, data associated with a program transmitted from a transmitting apparatus 1 of a broadcasting station are supplied via a satellite 2 to a receiving apparatus 3 installed in each home.
FIG. 2 shows an exemplary configuration of the transmitting apparatus 1. The transmitting apparatus 1 has a control section 11 which controls the inside of the apparatus. The control section 11 has a memory 12 for accumulating organization data. The organization data denotes the data associated with a schedule (a program table) for use in broadcasting programs. The control section 11 also has a clock 13, by which clocking the data transmission timing of each section is controlled.
A VTR (Video Tape Recorder) cart 14 is composed of a plurality of VTRs, a device for carrying and loading VTR tapes into these VTRs, and a shelf for accommodating these VTR tapes and, under the control of the control section 11, carries and sets predetermined VTR tapes from the shelf to the VTRs. Of the data reproduced from each VTR tape set to each VTR, video data are supplied to a video encoder 15 while audio data are supplied to an audio encoder 16.
The video encoder 15 and the audio encoder 16 encode the supplied data by a predetermined encoding algorithm, MPEG (Moving Picture Expert Group) for example, and output the resultant data to a multiplexer 17. An EPG (Electric Program Guide) generated by an EPG generating section 18 is also supplied to the multiplexer 17.
Under the control of a multiplexing control section 19, the multiplexer 17 multiplexes the supplied data. A standard by which the multiplexer 17 executes multiplexing is time-division multiplexing including MPEG2 TS (ISO13818-1) for example.
The multiplexing control section 19 receives information from the control section 11 to determine the PID (Packet ID) of each TS (Transport Stream) packet for transporting video and audio streams and outputs the determined PID to the multiplexer 17. On the basis of the PID supplied from the multiplexing control section 19, the multiplexer 17 sets the PID of each TS packet in which the supplied video and audio streams are stored.
The multiplexing control section 19 generates information associated with PSI (Program Specific Information) including PID information and supplies the generated information to the multiplexer 19. The multiplexer 17 includes the supplied PSI information in other signals to perform multiplexing.
The control section 11 controls each component of the transmitting apparatus 1 and, at the same time, converts the clock information provided by the incorporated clock 13 into a PCR (Program Clock Reference) to supply it to the multiplexer 17. Also, the control section 11 issues a command to the multiplexing control section 19 telling to which stream the PCR is to be added. In the description below, it is assumed that the PCR is attached to the video stream.
The multiplexing control section 19 specifies the same PID as the PID specified for the video stream as the PID of the transport packet to which PCR is added. The multiplexer 17 includes the supplied PCR into the transport packet of the video stream.
The output of the multiplexer 17 is supplied to an ECC (Error Correcting Code)/modulating section 20 to be added with an error correction code and modulated for transmission, the resultant data being outputted to an amplifying section 21. The amplifying section 21 amplifies the supplied data to a power level enough for transmission and transmits the amplified data as a radio wave via an antenna 22.
The data thus transmitted from the transmitting apparatus 1 are received by the receiving apparatus 3 via the satellite 2. FIG. 3 illustrates an exemplary configuration of the receiving apparatus 3. The receiving apparatus 3 has a control section 31 for controlling the inside of this apparatus. The control section 31 has a memory 32 for storing EPG and PSI information and a clock 33.
Radio waves (or radio signals) received at an antenna 34 of the receiving apparatus 3 are outputted to a front end 35. The signals are tuned in, demodulated, and error correction codes are removed from the signals to output the signals as a transport stream. The transport stream outputted from the front end 35 is outputted to a PSI filter 36, an EPG filter 37, an output PID filter 38, and a PCR PID filter 39. These filters each extract a transport packet including the specified PID from the supplied transport stream.
The PSI filter 36 extracts a transport packet which contains PSI from the supplied transport stream and outputs the obtained PSI to the control section 31. The control section 31 stores the received PSI into the memory 32.
The EPG PID filter 37 extracts a transport packet which contains an EPG from the supplied transport stream. The PID of the transport packet containing the EPG is supplied from the control section 31. On the basis of this supplied PID, the EPG PID filter 37 further extracts EPG information from the extracted transport packet and outputs the extracted EPG information to the control section 31. The control section 31 stores the received EPG information into the memory 32.
The output PID filter 38 extracts a transport packets which contains a video stream and an audio stream from the supplied transport stream. The PID of the transport packet containing the video stream and audio stream is supplied from the control section 31.
On the basis of the PID supplied from the control section 31, the output PID filter 38 extracts the video stream from the supplied transport packet and outputs the extracted video stream to a video decoder 40. Likewise, on the basis of the supplied PID, the output PID filter 38 extracts the audio stream from the supplied transport packet and outputs the extracted audio stream to an audio decoder 41.
The PCR PID filter 39 extracts a transport packet which contains a PCR from the supplied transport stream. The PID of the transport packet containing this PCR is supplied from the control section 31. On the basis of the supplied PID, the PCR PID filter 39 extracts the PCR from the supplied transport stream and supplies the extracted PCR to a STC (System Time Clock) 42. The STC 42 synchronizes its clock on the basis of the supplied PCR to generate a reference clock.
An OSD (On Screen Display) 43 generates a video signal, under the control of the control section 31 as required, and supplies the generated video signal to an adding section 44. The adding section 44 adds (or mixes) the video signal supplied from the OSD 43 to the video signal supplied from the video decoder 40 and outputs the resultant signal to a television receiver (not shown) connected to the receiving apparatus 3.
The receiving apparatus 3 receives a plurality of programs at the same time. The receiving apparatus 3 must provide a program requested by the user from among the plurality of received programs. The program selecting operation to be performed by the receiving apparatus 3 will be described below with reference to the flowchart shown in FIG. 4. The processing described in the flowchart shown in FIG. 4 is executed when the receiving apparatus 3 is powered on by a remote controller (not shown) for example.
In step S1, the control section 31 of the receiving apparatus 3 determines whether or not any one of the PSI information and the EPG information stored in the memory 32 is older than the current time as information and lacking as information. Namely, the control section 31 compares the PSI and EPG information stored in the memory 32 with the clock information indicated by the clock 33 to determine whether or not the information of PSI and EPG is older than the current time and lacking as information.
If any one of the PSI information and the EPG information stored in the memory 32 is found older than the current time or lacking as information in step S1, then the procedure goes to step S2; if the information is found not older than the current time or not lacking as information, then the procedure goes to step S3 by skipping step S2.
In step S2, the PSI and the EPG are updated. The control section 31 commands the front end 35 to receive a default channel. On the receiving apparatus 3, a predetermine channel is set as default beforehand. The front end 35 tunes in the frequency/band on which the default channel is transmitted, demodulates the signal, performs error correction on the signal by use of an error correction code, and outputs the resultant signal as a transport stream.
The transport stream outputted from the front end 35 is supplied to the PSI filter 36 and the EPG PID filter 37. The transport stream is also supplied to the output PID filter 38 and the PCR PID filter 39; in this case, however, the supplied transport stream is not used in these filters (or not processed by these filters).
The PSI filter 36 extracts the PSI information from the supplied transport stream and supplies the extracted PSI information to the control section 31. The PSI supplied to the control section 31 is stored in the memory 32. In this case, the information associated with the number of programs to be broadcast at the same time (1 in this example), the number of video/audio streams for each program (1 each in this example), and a method of transmitting the PID and EPG of transport packets carrying the PID and PCR for each stream is supplied to the control section 31.
Since the PID containing PSI is determined beforehand, the control section 31 need not supply the PID to the PSI filter 36. The control section 31 supplies the value of the PID of the transport packet containing EPG to the EPG PID filter 37. By use of the supplied PID value, the EPG PID filter 37 extracts EPG data therefrom from the transport packet and supplies the extracted EPG data to the control section 31. The EPG information supplied to the control section 31 are stored in the memory 32.
The PSI and EPG information is contained in each transport stream. In the control section 31, the above-mentioned operation is always performed, and always updating the PSI and EPG information.
As required or in response to a user command from a remote controller not shown, the control section 31 extracts and manipulates the EPG information and commands the OSD 43 to converts the resultant information into a video signal. The video signal generated by the OSD 43 is mixed by the adding section 44 with the output signal of the video decoder 40 and the resultant signal is outputted.
In step S3, the control section 31 reads the channel viewed immediately before the last power-off sequence from a non-volatile storage device not shown for example. It is assumed here that channel A was viewed immediately before the last power-off sequence.
The control section 31 commands the front end 35 to receive channel A. The front end 35 tunes in the transmitted frequency/band of channel A, demodulates the signal, performs error correction on the demodulated signal by error correction code, and outputs the transport stream.
The transport stream outputted from the front end 35 is supplied to the PSI filter 36, the EPG PID filter 37, the output PID filter 38, and the PCR PID filter 39.
As described above, the PSI filter 204 extracts PSI information from the supplied transport stream and supplies the extracted PSI information to the control section 31, upon which the PSI stored in the memory 32 is updated. As described above, the EPG PID filter 37 also extracts EPG information from the transport packet by use of the value of the supplied PID and supplies the extracted EPG information to the control section 31. The control section 31 updates the EPG information stored in the memory 32.
The control section 31 supplies to the output PID filter 38 the value of the PID of the transport packet carrying a video stream and the value of the PID of the transport packet carrying an audio stream. At the same time, the control section 31 supplies the value of the PID of the transport packet containing an EPG to the EPG PID filter 37. The control section 31 supplies the value of the PID of the transport packet containing a PCR to the PCR PID filter 39.
The output PID filter 38 extracts the video stream and the audio stream from the transport packet by use of the supplied two PID values. The video stream is supplied to the video decoder 40 while the audio stream is supplied to the audio decoder 41.
The video decoder 40 converts (or decodes) the supplied video stream encoded by a predetermined encoding scheme into a video signal and outputs it. Likewise, the audio decoder 41 converts the supplied audio stream into an audio signal and outputs it.
The PCR PID filter 39 extracts a PCR from the transport packet by use of the given PID value and supplies the extracted PCR to the STC 42. The STC 42 synchronizes the own clock with the supplied PCR. The internal clock generated by use of the PCR is used as a synchronous clock for the video decoder 40 and audio decoder 41.
In step S4, the control section 31 determines whether or not a channel change command has been issued by a user not shown through a remote controller not shown or a button for example arranged on the receiving apparatus 3. If the channel is found changed, the procedure goes to step S5. If the channel is found not changed, the procedure returns to step S4 to repeat the processing therefrom.
If the command is found issued by the user in step S4, this command is sent to the control section 31, which in turn commands the front end 35 to receive the specified channel. Consequently, in step 5, the transport stream outputted from the front end 35 is processed as described above, thereby outputting the program of the newly selected channel. When this processing comes to an end, the procedure returns to step S4 to repeat the processing therefrom.
Thus, the user-specified program is provided to the user from among the plurality of channels (programs) received by the receiving apparatus 3.
The following describes channels which are transmitted from the transmitting apparatus 1 to the receiving apparatus 3. In the following example, the case in which only one channel A is provided over 24 hours as shown in FIG. 5. It is assumed that the band prepared as broadcasting facilities be 24 Mbps for a whole day. This value is the bit rate before performing error correction and modulation and the bit rate of the data to be transferred from the multiplexer 17 to the ECC/modulating section 20.
FIG. 6 illustrates an enlarged portion around a prime time of October 10 shown in FIG. 5, with program divisions and program names added. The prime time denotes a time zone in which audience rate is higher than in other time zones; for example, a time zone from 19:00 to 23:00.
In channel A, “program A” is provided from 18:00 to 19:00 of October 10. Likewise, “program B” is provided from 19:00 to 20:00, “program C” is provided from 20:00 to 21:00, and “program D” is provided from 21:00 to 23:00.
A program provision (broadcasting) schedule listed with necessary information as shown in FIG. 7 is called organization data for example. Organization data are a collection of plural records for each program. Each record for each program is constituted by six fields “channel,” “date,” “start time,” “length,” “program name,” and “attribute.”
The organization as described above are set to the control section 11 by the administrator not shown of the transmitting apparatus 1 and stored in the memory 12. The organization data are used to control the transmitting apparatus 1 in its entirety.
However, the above-mentioned conventional configuration has a problem that, as described above, channel A provides programs by use of a transmission path having a band of 24 Mbps all day, which indicates that the program provision is performed on the same band regardless of prime time and other time zones, resulting in the ineffective usage of the band.